Before Danny Lyon graduated from the University of Chicago in 1963, he was well on his way to a career that would transform the very idea of what photography is.

The summer before his senior year, he worked as a staff photographer for the Student Nonviolent Coordinating Committee, the civil-rights-activist group. He traveled South and made gorgeous shots of protesters dropping to their knees on the streets in prayer, or being hauled off to jail by the cops. But Lyon was no objective observer: He landed in jail in Georgia that year with other activists, including the Rev. Martin Luther King Jr.

And back in Chicago, while still an undergrad, he rode with the Chicago Outlaws motorcycle gang. Lyon was a club member in good standing, but he was also a photographer, and once again, he took beautiful black-and-whites. This time, the pictures were of bikers idling by their machines, or carrying the coffin of a fallen rider, or roaring down a highway into America.

"I was a bike-rider, a photographer and a history student, probably in that order," Lyon wrote many years later in Memories of Myself.

Lyon, who's making two appearances in Tucson this weekend (see the info box for details), published the civil-rights photos before he graduated, and he published The Bikeriders as a book in 1968, when he was just 26 years old. The still-influential civil-rights photos were praised early on, but The Bikeriders was "the project that put Danny on the map," says Terry Etherton, who is exhibiting the motorcycle work at Etherton Gallery.

But Lyon didn't stop with the bikers. Before the 1960s were out, he had documented the historic lower-Manhattan neighborhood that was swept away to make room for the doomed Twin Towers. He photographed Uptown Chicago, a district of poor white migrants from the South. And he made his most-acclaimed work of all, Conversations With the Dead, photographs of Texas prisons that make you want to fall down on your own knees and thank God you never committed a crime in the Lone Star State.

By 1970, Etherton says, Lyon became the youngest University of Chicago grad ever to be named a "distinguished alumnus."

The self-taught Lyon is not a strict documentarian. He's a politically engaged participant in whatever he's photographing. (He's also made movies in the same vein.) He befriended many prisoners in Texas, and his photographs—documenting segregation in the state's jails—were used in a federal lawsuit that helped dismantle the system of keeping black prisoners and white prisoners apart, Etherton says.

Often described as a new kind of journalist—or a new photographer—he has made a career of giving voice to the voiceless, of picturing people whose lives were never going to make it into Life magazine. At the time, his personal engagement with his subjects was revolutionary.

The Outlaws photos have shock value, to be sure. They're filled with tough guys in leather jackets and chains, their very looks a challenge to a button-down America still tethered to the 1950s. (The book, which quickly became a cult classic, is believed to have inspired the 1969 movie Easy Rider.) What they do is devilish and dangerous, as the solemn photos of "Renegade's funeral, Detroit," make clear.

But The Bikeriders pics are also beautifully rendered character studies, heartbreaking photos of young working-class men and women whose lives are cramped and constrained when they aren't revving the engines and riding the road.

"Brucie, his CH, and Charlie, McHenry, Illinois" pictures a young man with the cool anomie of James Dean, crouched in front of his big bike. He looks straight at the camera—moody, defiant, uncertain—and his presence, his selfhood, is recorded for all time.

"Sparky and Cowboy (Gary Rogues), Schererville, Indiana," are in their leather jackets and their insignia, but they pose in front of innocuous wooden siding. Stripped of their cycles, they're shy, almost self-effacing, a couple of young guys without much traction in a world that scorns them. Sparky even turns his head sideways, averting a direct gaze.

With the setting being the Midwest, the photos also picture at least one white picket fence and a couple of neighborly porches, where the Outlaws gather to socialize. The most-tender pictures show the bikers with their families. Cowboy, from "Sparky and Cowboy," reappears as a dad in "Cowboy at a Rogue's Picnic, South Chicago." He stands in a park, right by the picnic tables, with a gaggle of kids in the grass at his feet. A slight, contented smile plays on his lips.

The women are intriguing. They seem to be mostly along for the ride, babes on the back of a bike, but Lyon also captures their longing. "Prairieville, Louisiana" is a striking full-length portrait of a young woman in a cheap, ill-fitting dress. She stands in an empty field, mostly alone. Her teased-up hair is stiff and sky-high, but her face is vulnerable, wistful.

"Memorial Day run, Milwaukee" is a stunner that inexplicably did not appear among the 49 photos in the original book. (Etherton added it for this show.) Picturing the biker from the back, it gives its full attention to his female rider. All flying blond hair and white-rimmed sunglasses, she turns and looks back, frowning, as she sails away.

Some of the most-glorious photos picture the urban Outlaws basking in the open air of the countryside. In "Outlaw Camp, Elkhorn, Wisconsin," the riders are clustered at a distance in a meadow, dark figures along a high horizon line. The wide field spools down from there, an infinity of grasses and dandelions.

And, of course, the shots of the riders riding the open road are joyful paeans to movement and escape. In "Crossing the Ohio, Louisville," "From Dayton to Columbus, Ohio" and "Route 12, Wisconsin," the motorcyclists sail over the blacktop. They chase the American dream, lighting out for the territories.

For a 1980s glimpse of motorcyclists, Tucson-style, see photographer Ann Simmons-Myers' Bikers at the Temple Gallery. These bikers love their bikes as much as their Chicago brethren do. "Terry With His Sportster" is a triptych with three views of Terry caressing his bike under a palm tree in a quintessentially Tucson yard.

Tattooed and tattered and battered though they are, the Tucsonans seem even more domesticated than the Chicagoans. Simmons-Myers records a biker wedding in a park ("Wedding Guests"), and two tough-looking male bikers caring for a newborn in the triptych "The Babysitters, Chromebeard with Dickie Dody and Heather." The men give the little girl a bottle. And in the final sequence, the aptly named Chromebeard gently pulls up her little legs and begins to change her diaper.